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egulations and procedures. Non-U.S. missions must register their frequency usage
internationally through their appropriate spectrum management agencies.
Early in the mission planning cycle, NASA projects must contact the appropriate center
spectrum manager to get NTIA authorization to transmit. The NASA Center Spectrum
Managers are responsible for management of the RF equipment licensing process, and
are the final authority on the selection of the appropriate frequencies for all NASA RF
equipment. Amongst other duties, these center managers will facilitate the licensing of
RF equipment by coordinating with national and international organizations in: 1)
making frequency selections, 2) evaluating RF equipment against applicable national
and international RF standards, 3) performing RF analyses, and 4) completing
frequency authorization applications to the NTIA.
Goddard Procedural Requirements (GPR) 2570.1, Spectrum Management and Radio
Frequency (RF) Equipment Licensing, provides GSFC missions with the requirements
for Radio Frequency (RF) equipment licensing in accordance with NASA Policy
Directive (NPD) 2570.5, NASA Electromagnetic Spectrum Management. In accordance
with NPD 2570.5, all missions must comply with domestic (NTIA) and international (ITU)
regulations and SFCG recommendations.
D.3 Power Flux Density (PFD) Considerations
PFD limits on the surface of the Earth are the primary means to prevent harmful
interference to terrestrial systems operating in bands shared with the TDRSS Space
Network. In those bands which are shared on a primary basis between the space and
terrestrial services, the PFD limits are incorporated into the Radio Regulations. PFD
levels should be calculated early, preferably during the mission planning and system
design phase, in order to determine whether or not the PFD limits would impose any
unsatisfactory system requirements or operational constraints. For example, many
missions with high gain antennas opt to delay the start of transmissions until some
period of time after the TDRS comes in view over the horizon in order to satisfy the PFD
limits. Additionally, mission planners are strongly urged to consider that satellite
subsystems and components often exceed specifications and this can result in PFD
levels being exceeded.
The applicable PFD limits for the TDRSS S-Band, Ku-band, and Ka-band links are
provided in Paragraph D.3.1. Paragraph D.3.2 describes the impact of exceeding the
PFD limits. Paragraph D.3.3 provides the equations used to determine PFD levels.
Paragraph D.A.1 provides an example application.
D.3.1 PFD Limits
Power Flux Density limits are imposed on NASA missions by both the NTIA and the
ITU. Although largely similar, there are a number of differences in the requirements,
which can result in a mission meeting one requirement but not the other. The
consequences of failure to meet NTIA and ITU PFD limits are outlined in paragraph
D.3.2. This section lists the NTIA and ITU PFD limits in the TDRSS forward and return
link bands.
Revision 10 D-2 450-SNUG